1. Field of the Invention
The present invention relates to a holding apparatus for holding a plate-like member such as a semiconductor wafer, and a method for holding the member.
2. Description of the Related Art
In the step of machining or inspecting a semiconductor in the process of the manufacture of a semiconductor, e.g., in the step of measuring electrical characteristics of a wafer using a wafer prober, a semiconductor wafer conveyed by a conveyor belt or a robot arm from a wafer carrier is placed on a convey arm after performed prealignment by way of positioning a flat orientation, and is transferred from the convey arm to a chuck for supporting the semiconductor wafer while chucking it.
In the wafer transfer step, a plurality of pins of projecting members embedded in the chuck project from the surface of a holding table of the chuck, and the semiconductor wafer is transferred onto the projecting pins from the convey arm. The projecting members are moved downward and the pins are concealed in the chuck, and then the wafer placed on the pins are chucked and fixed on the upper surface of the holding table. In this state, the chuck is intermittently moved for each wafer so that a large number of probes supported to a probe card correspond to a large number of electrodes on each chip of the wafer.
Such a holding apparatus is disclosed in, for example, Japanese Utility Model Publication No. 62--6691.
However, in the conventional holding apparatus, a semiconductor wafer as a plate-like member is transferred onto the plurality of pins projecting from the holding table, and thereafter, the pins are moved downward. Therefore, the speed of downward movement of the pins and that of the semiconductor wafer which receives an air resistance differ from each other, with the result that the wafer floats. In this case, the semiconductor wafer performed prealignment is placed on an offset position on the holding table, and in the worst case, may be dropped from the holding table.
When the wafer is transferred from the convey arm to the pins of the projecting members, noise is generated as the distal ends of the pins, which are being moved upward, collide against the wafer.